Immunotherapies that have the potential to eradicate reservoirs of viral infection may be a useful means to suppress or cure HIV/AIDS in combination with current antiviral drug therapies that only inhibit viral replication. T cells expressing chimeric immune receptors (CIRs) through gene modification can be redirected to kill tumor or virus-infected cells. Several forms of CIRs specific to HIV antigens have been developed. So far, the most promising anti-HIV CIR and the only one that has been tested in clinical trials is CD4zeta (CD4?), which is specific to HIV-1 gp120 antigen in MHC nonrestricted fashion through its CD4 extracellular domain. However, the adoptive transfer of autologous CD4?-T cells to HIV/AIDS patients failed to control the viral infection in clinical trials, despite the persistence of a percentage of adoptively transferred CD4?-T cells in recipients for up to 1 year after infusion. The mechanisms of failure are unknown. To date, all anti-HIV CIRs have been simple TCR-signal (Signal 1) molecules. Results from our laboratory and others have demonstrated that CIRs can be enhanced in their potency in T cell activation by providing co-stimulatory signal (e.g., CD28; Signal 2). Our preliminary results indicated that CD4-based anti-HIV CIRs with TCR Signal 1 alone or Signal 1+2 (i.e., 1st generation CD4? and 2nd generation CD4CD28? CIRs that include Signal 2) expressed equally well on retrovirally transduced human T cells. The rationales of this proposal are (1) to enhance the potency of anti-HIV CD8+ designer T cells with the CD4-based anti-HIV CIR by including CD28 signaling, and (2) to optimize the design of CD4-based CIRs with Signals 1+2 (CD4CD28?). We will construct and compare a panel of CD4-based CIRs of different designs with or without CD28 signaling, including three CD4CD28? of different designs, for their potencies in activation upon antigen stimulation, susceptibility to induction of anergy and susceptibility to HIV infection. We will also evaluate their in vivo immunotherapeutic efficacy in targeting HIV antigen (gp120)-expressing cells in a xenografted mouse model. If proven more potent than the 1st generation anti-HIV designer T cells armed with anti-HIV CIR CD4?, the new 2nd generation of designer T cells with optimal CD4CD28? design will serve as a new class of immunotherapy reagents to enhance the clinical outcome of adoptive transfer of specific T cells for HIV/AIDS. [unreadable] [unreadable] [unreadable] [unreadable]